Progress 10/01/11 to 09/30/12
Outputs
OUTPUTS: The primary activities of this award were scientific training for undergraduate students and research technicians, and mentoring by PI Raguso. The award employed Stephanie Topp (1 Oct 2011-1 Feb 2012) and then Michael Wolfin (10 Feb - 15 Aug 2012) as lab technicians, primarily responsible for the care and maintenance of our Manduca sexta moth colony - the source of eggs for behavioral assays with wasps - and for oversight of behavioral assays in y-mazes. PI Raguso provided Topp and Wolfin with training on designing behavioral assays, managing students and rudimentary statistical analyses, and encouraged their participation in journal clubs, noon seminars and other forms of employee enrichment. Topp moved on to a lab tech job at SUNY Albany, and Wolfin entered the Entomology PhD program at Cornell at the end of August. Two undergraduate students contributed to this project; Rebecca Earl, a graduating senior (Oct 2011-May 2012) and Margaret Henderson, a rising sophomore (June-Sept 2012). Rebecca focused primarily on Y-tube assays and optimization of experimental conditions as her senior year research project, whereas Margaret explored another aspect of wasp behavior, using no-choice assays in which female wasps were presented with artificial moth eggs in which appearance and chemistry were decoupled experimentally. Henderson remains enrolled at Cornell, whereas Earl graduated in May and took a job as a field ornithological researcher on Alcatraz Island, in San Francisco bay, CA. The dissemination of our results took the form of a poster presentation and outreach activities. Rebecca presented her Y-tube data in a poster at the Cornell Undergraduate Research Board symposium in April 2012, and participated (with Raguso and Topp) in a demonstration of the effects of relative humidity on insect behavior at the October 2011 Insectapalooza Open House. Margaret (along with Wolfin) participated in Insectapalooza this past October (2012). Margaret competed for and won a Morley student award ($1000) in order to continue her studies as an independent student project. PARTICIPANTS: The primary participants in the project (research technicians Stephanie Topp and Michael Wolfin; undergraduate researchers Rebecca Earl and Margaret Henderson) were identified in the Outputs section, along with the opportunities for professional development. A postdoctoral fellow, Dr. Joaquin Goyret, was consulted specifically for measurements of relative humidity. Partners on the grant included Drs. Michael Hoffmann, Jeffrey Gardner and Sylvie Pitcher, in whose laboratory the bioassays were performed at the Cornell Entomology Insectary. TARGET AUDIENCES: As described in Outputs, we made presentations of our results in two different public forums. The Insectapalooza event is an annual (October) open house outreach event hosted by Cornell's Entomology Department, and typically draws 1500-3000 visitors from greater Tompkins County NY. Traditionally, these visitors are children with their families. The CURB symposium is an annual (April) event in which Cornell undergraduates present their research projects either as posters or as brief power point talks, to an audience of their peers and professors. 90 abstracts were included in the 2012 CURB program, indicating strong participation by Cornell undergraduates. This event typically is attended by several hundred students and faculty. PROJECT MODIFICATIONS: We originally planned to utilize a 4-way olfactometer as an experimental arena, but preliminary trials revealed that this horizontal arena and its setting in Raguso's lab were not ideal for wasp behavior, due to their small size and preference to move vertically and towards the light. Instead, we moved the experiments back to the Insectary, where the Trichogramma colony is located and previous trials had been successful. The first half of the award period was spent working with wasps in different kinds of Y mazes in order to optimize experimental protocol. In the end, the use of vertical Y-mazes under strong lighting, in warm (28-30C) room temperatures was found to be most effective. Rebecca performed 4 sets of binary choice assays between different levels of relative humidity (RH): 20% vs. 20, 45, 75 or 90%, taking care to randomize the order of the assays so that specific treatments were not confounded with day (and specific ambient conditions). She found that wasps do not show strong preferences at very high (90%) or very low (20%) RH, and are as likely not to move or choose an arm of the Y-maze. However, at intermediate RH levels, wasps showed strong (two -four fold) preference for higher (45 or 75%) RH levels. These results were consistent with our expectations from previous pilot studies. Unfortunately, just as Rebecca got the hang of the bioassays and had begun to increase sample sizes for all comparisons, maintenance workers at the Insectary closed access to the laboratory to remove ceiling asbestos for a period that extended through Rebecca's graduation. The last part of the award period consisted of Margaret's exploratory comparisons of real vs. artificial moth eggs, in an effort to experimentally decouple humidity (from the leaf surface) from egg color and odor. Initial results were promising, revealing that solvent extracts of eggs added to clay surrogate eggs of the correct green color elicited attraction and oviposition efforts by female wasps. Margaret will continue this study with video recordings, using funds awarded through the Morley fellowship.
Impacts
Changes in knowledge: Through Y-maze binary choice tests run at different levels of relative humidity, we demonstrated that Trichogramma female wasps prefer to enter and remain in the more humid arm of the Y-maze when humidity levels are intermediate (45 or 75 percent), but do not show preferences when humidity is very low (20 percent) or very high (90 percent). This finding is consistent with pilot data from previous studies, and confirms that the wasps should not be released on very dry or extremely humid days, as they will be unlikely to search actively for pest insect eggs. We also learned, through no-choice assays performed in Petri dishes, that female wasps are visually attracted to Manduca eggs or similarly turquoise-colored clay model eggs of the same size. However, they are less likely to oviposit into those eggs if they have been hexane extracted (odor removed) or the clay egg models have not had odor added to them. Thus, the chemistry of the moth eggs appears to be an important check point in prompting female wasps to parasitize them as hosts. Through this award, Rebecca Earl came to understand how to design, perform and be responsible for a research project, and drew motivation to pursue a career in biological research. She was able to gain the confidence to apply for exciting advertised positions in field research, and learned how to present a poster of her results to her peers in the lab and during the CURB symposium.
Publications
- No publications reported this period
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